금형면 자동 다듬질 전문가 시스템 개발에 관한 연구-Ⅱ : 통합 연마 파라미터를 사용한 최적 가공 구현 및 전문가 시스템 구축

민헌식,이성환,안유민,조남규,한창수 한국공작기계학회 2002 한국생산제조학회지 Vol.11 No.1

To reduce the cost and increase reliability of die and mold products, automation of the finishing (polishing) process is essential. A major element of automation is a reliable database and a knowledge base for polishing status. This paper presents a polishing expert system which can determine optimal polishing sequences and conditions by using an empirical formula and an experimental database. The simplex method was used for the cure fittings of the experimental results. Also a graphical user interface, which visualizes the optimized results, was developed.

레이저 용융 절단 해석 프로그램 개발

민헌식,이성환 한국공작기계학회 2002 한국생산제조학회지 Vol.11 No.3

Though the laser cutting process is increasingly used in industry, a process automation and systematic database is still yet to be developed. In this study, as the fundamental step toward the construction of a reliable process expert system, a laser cutting quality monitoring/analysis system is developed based on simulation and experimental results. The relations between laser process parameters and laser cutting surface quality parameters such as kerf geometry, striation, surface roughness and dross formation are characterized and analyzed. A graphical user interface is used to visualize the results.

AE센서를 이용한 레이저 용융 절단 모니터링

민헌식,이성환,안선응 한국공작기계학회 2002 한국생산제조학회지 Vol.11 No.3

As laser cutting process is widely used in industry, an automated on-line process control system has become very important. In this paper, development of a laser cutting monitoring system, which is regarded as the fundamental step toward automation of the process, is presented. Acoustic emission and an artificial neural network were used for the monitoring system. With given process parameters including laser power and scanning speed, the system can predict the suitability of laser beam for the cutting of a stainless steel (STS304) plate.

北韓 憲法上의 權力構造에 관한 硏究 : 北韓의 新憲法을 中心으로 with Special Referance to the New Constitution of the North Korea

林憲素 牧園大學校 法學硏究所 1993 法學論叢 Vol.1 No.-

금형면 자동 다듬질 전문가 시스템 개발에 관한 연구-Ⅰ : DB 구축을 위한 회전 및 진동 연마 가공의 실험적 연구

민헌식,이성환,안유민,조남규,한창수 한국공작기계학회 2002 한국생산제조학회지 Vol.11 No.1

In manufacturing die and mold, polishing is important as it takes as mush as 50% of the production cost. In this research, an attachable type polishing device to a CNC machining center was developed. Experiments were done with a specially designed rotation type polishing device. Also an ultra-sonic (Vibration type) waving device was introduced to acquire finer surface finishes. From the constructed data base based on the experimental results, it is shown that optimal polishing conditions are generated by the combined use of the rotation type tool and the vibration type tool.

Thermodynamic and spectroscopic identification of aldehyde hydrates

Huen Lee,Hyery Kang,안윤호,Dong-Yeun Koh 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.6

It has been reported that some aldehyde compounds have formed simple sII clathrate hydrates without help-gas molecules, showing a self-forming effect. However, the structure of aldehyde hydrates is quite unstable due to the “gem-diol reaction”. According to the previous studies, the aldehyde hydrate slowly decomposes at atmospheric condition with the conversion of aldehyde to gem-diol. We investigated binary aldehyde (acetaldehyde, propionaldehyde, and isobutyraldehyde)+methane clathrate hydrate with spectroscopic and thermodynamic analyses. Similar to the simple aldehyde hydrate, the binary hydrates also formed a sII hydrate. During the hydrate formation process, we found that most of the aldehydes converted to gem-diols and were then incorporated into the large cages of the sII hydrate. Depending on the equilibrium constant of the gem-diol reaction caused by the molecular structures of the three aldehydes, different phase equilibrium curves of aldehyde+methane hydrates were obtained.

Transactions : Suggested and Preferred Amount of Clothing in a Winter Indoor Condition

( Huen Sup Shim ),( Woon Seon Jeong ) 한국의류학회 2011 한국의류학회지 Vol.35 No.12

This study proposes the suggested amount of clothing (SAC) and examines the preferred amount of clothing (PAC) for thermal comfort in mild cold conditions. Six male and nine female college students were systematically exposed to mild cold conditions by reducing the amount of clothing (Step I, 1.2clo → Step II, 1.0clo → Step III, 0.8clo → Step IV, 0.7clo). The subjects were then asked to adjust the amount of clothing to attain overall thermal comfort until they maintained thermal comfort for 10 minutes without changing the amount of clothing (Step V). The experiment was carried out in a climatic chamber at 19.5℃, 50%R.H. Body composition was measured and individual cold climate adaptability was surveyed before starting the experiment. Rectal temperature (T(re)), skin temperature (T(sk)), and oxygen consumption (VO2) were measured and the overall thermal sensation was voted in each step. PAC was obtained from the garments weight selected by each subject in Step V. SAC was proposed based on the change of oxygen consumption (ΔVO2). As a result, males showed higher T(sk) and greater VO2 than females (p<.01). SAC obtained from VO2 were 652.0 (SE 3.9) g/m2 for males and 766.0 (SE 2.5) g/m2 for females and it was significantly different between groups (p<.01). PAC of males and females were 1.6 and 1.5 times heavier than SAC. In conclusion, females were more sensitive to the cold stress and recommended larger amount of clothing than males.

One-dimensional approaches for methane hydrate production by CO2/N2 gas mixture in horizontal and vertical column reactor

Huen Lee,Yutaek Seo,Yeobum Youn,Minjun Cha,Juwoon Park,Minchul Kwon 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.5

The recovery of methane gas from methane hydrate bearing sediments was investigated by using a continuous stream of a CO2 and N2 gas mixture. A long cylindrical high-pressure reactor was designed to demonstrate the recovery of methane from methane hydrate bearing sediments, and the injection rate of the gas mixture was controlled to monitor the amount of recovered methane from methane hydrates. The recovery efficiency of methane gas from methane hydrates is inversely proportional to the flow rate of the CO2 and N2 gas mixture. Methane hydrates were synthesized by using two different sediments, having particle size distributions of 75 to 150 μm and 45 to 90 μm with the same porosity, and the recovery efficiency of methane from methane hydrates was also monitored. We confirmed that there is no significant difference in the replacement characteristics by using these two different sediments. Horizontal and vertical flows of the CO2 and N2 gas mixture were applied to monitor the effect of flow direction on replacement characteristics. We also confirmed that a similar amount of methane was recovered in horizontal and vertical flows of the CO2 and N2 gas mixture at the same flow rate. The present study may help in establishing the process variables for recovering methane gas from methane hydrate bearing sediments in offshore conditions.

Phase behavior of gas hydrates in nanoporous materials: Review

Huen Lee,Daeok Kim 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.7

−A precise understanding of phase behavior for a variety of both artificial and natural processes is essential to achieving scientific and technological goals. There has been growing research interest in gas hydrates confined in nanoporous media aiming to simulate and analyze the unique behavior of natural gas hydrates in sediments. Moreover, the appearance of peculiar properties due to the confinement effect stimulates research on gas hydrate technology for gas separation, such as CO2 capture from versatile pre/post combustion emissions. In spite of their importance, reliable phase equilibrium data on gas hydrates confined at a nanoscale are scattered throughout the literature, while those in bulk state are abundant. Accordingly, we surveyed the previous studies on the phase behavior of gas hydrates in various nanoporous materials to include and provide valuable information and knowledge for start-up researchers in various gas hydrate fields.

Experimental verifications of Mpemba-like behaviors of clathrate hydrates

Huen Lee,안윤호,Hyery Kang,Dong-Yeun Koh 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.6

The exact mechanism of the Mpemba effect of water was recently investigated microscopically and explained on the basis of the cooperative relationship between intramolecular polar-covalent bonds (O-H) and intermolecular hydrogen bonds (O :H). We posited that this relationship might exist in clathrate hydrates since they consist of hydrogen-bonded host water frameworks and enclathrated guest molecules. The formation of tetrahydrofuran (THF) hydrate, which is the simplest clathrate hydrate, was investigated by using differential scanning calorimetry and Raman spectroscopy. THF hydrates show the Mpemba effect at lower initial temperatures, but formation times were delayed at higher initial temperatures because the evaporated THF molecules should be liquefied to correspond to the stoichiometric concentration of guest molecules to form sII clathrate hydrates. However, even though the formation time was delayed at higher initial temperatures, the rates of heat emission during THF hydrate formation, measured in a bulk state, roughly increased as the initial temperature increased. Moreover, we observed that the O : H stretching phonons of water in the THF hydrate showed a blue shift, and the O-H stretching mode showed a redshift as temperature decreased. Both the rate of heat emission and the Raman shift of these two bonds imply that a cooperative relationship between the covalent bond and the hydrogen bond exists in THF hydrate as pure water. The formation kinetics of THF hydrate therefore might depend on its initial temperature, thus showing Mpemba-like behavior.